1. Field of the Invention
The present invention is directed to vertical shaft furnaces and more specifically to a top sealed vertical shaft furnace.
2. Prior Art
In conventional vertical shaft furnaces of the type used for smelting ores the top of the furnace is customarily provided with hopper means for introducing the charge into the furnace to form the burden which moves downwardly through the furnace to the combustion zone adjacent a plurality of circumferentially located tuyeres through which an air blast is introduced. The combustion gases rise upwardly through the furnace and collect in the top space between the top of the burden and the hopper means. An exhaust conduit or "downcomer" is provided in this top space for the removal of the gaseous effluents.
An example of such a furnace is the well known blast furnace used for the production of pig iron. The blast furnace is charged with a suitable mixture of coke, limestone and iron ore. The blast furnace process is based upon the counterflow of gases and solids. As carbon monoxide, nitrogen and hydrogen flow upward from the combustion zones, oxygen is acquired from the descending charge. In the reduction of iron ore, a portion of the carbon monoxide is converted to carbon dioxide and similarly a portion of the hydrogen is converted to water vapor. The inert nitrogen from the air used in combustion passes through the furnace with little change. Its concentration is, however, decreased by reactions such as direct reduction and solution loss which increase the volume of carbon monoxide in the gas stream. Similarly, the evolution of carbon dioxide from the limestone also dilutes the nitrogen. All of the gases and vapors produced collect at the top of the furnace and are removed through the "downcomer".
The Ebner U.S. Pat. No. 1,924,842 broadly discloses the idea of locating the outlet conduits immediately below the stock line to prevent the entry of dust or other particulate matter present in the air space above the stock line into the outlet conduits.